1. Field of the Invention
The present invention relates to a Read Only Memory (ROM) circuit, and more particularly, to a ROM circuit being subject to debugging/updating and a method thereof.
2. Description of Related Art
In a microprocessor system, a memory unit can be generally classified into two major categories: random access memory (RAM) and read only memory (ROM). A RAM is versatile, i.e. when supplying power is off, the data stored in the RAM is diminished, and thus a RAM is multi-writable. Yet a ROM is non-versatile, i.e. data stored therein stays even when supplying power is off, therefore suitable for storing BOOT program or BIOS code of a computer system. Since a ROM is non-versatile, the data therein cannot be modified once data is written. Therefore, modification of program/data stored in the ROM is hardly performed even a ROM is defective. Besides, data stored in ROM cannot be subjected to debugging or updating.
Electronic products, such as Erasable and Programmable ROM (EPROM), Electrically Erasable and Programmable ROM (EEPROM) and flash memory, serve limited modifying/updating flexibility, yet specific equipment or geometrical disposition is required to perform modifying/updating of program/data. Therefore, application scope of which is limited. For example, for a ROM of a Digital Signal Processor (DSP), it is not possible to debug/update the stored data with UV irradiation.